用于AMS测量重核素的飞行时间探测器性能的改进

Improvement of the TOF for accelerator mass spectrometry measuring heavy nuclide

自然界中极其微量的长寿命锕系元素236U、237Np、239Pu、240Pu、242Pu和244Pu在核保障中有极其重要的作用,为满足锕系元素236U高灵敏测量的需要,通过改进探测器结构、设计透射率高的碳膜支架和选用低电阻率的SBD作为时间停止探测器等多方面工作,对基于中国原子能科学研究院加速器质谱(AMS)的飞行时间探测器(TOF)性能进行改进。实验结果表明,改进后的TOF测量236 U的时间分辨由原来～980 ps提高到～500 ps。改进后的TOF完全能够把236U与其干扰同位素235 U、238 U鉴别开,AMS测量灵敏度236 U/238 U好于10-11,满足测量要求。

The naturaly ultra-trace actinide nuclide 236U, 237 Np, 239pu, 240pu, 242pu and 244pu are very important in nuclear safeguard. In order to meet the need of the high sensitivity measurement of 236U with accelerator mass spectrometry （ AMS）, a HI-13 accelerator at China Institute of Atomic Energy （CIAE）, was up-graded by optimizing the time resolution of the time of flight detector （TOF）. The TOF time resolution for 236U was improved from 980 ps to 500 ps. Which is sufficient to separate 236U from the isotope 23SU and ~35U, with a measurement sensitivity for 236U/23SU lower than 10-11.